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Questions tagged [dependencies]

The tag has no usage guidance.

4
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0answers
61 views

Can the Chase test algorithm only modify attributes on the right side of a functional dependency?

I'm attempting to apply the Chase Algorithm to determine if a decomposition is a lossless join decomposition. Functional Dependencies = {A → C, B → D, C → D, DE → C, CE → A} Here is my initial ...
2
votes
1answer
36 views

Can anyone help me understand the following paragraph?

I was reading Database Systems Design, Implementation and Management by Carlos Coronel. In the chapter of Normalization after he explained 3NF, he writes The existence of multiple candidate keys ...
0
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0answers
37 views

how to find out if it is safe to uninstall an application from a production sql server?

I noticed Microsoft Office components installed in a production SQL Server Box (which is part of an availability group - currently the principal) OS is microsoft windows server 2012 r2 datacentre, ...
2
votes
1answer
50 views

Questions Concerning the Chase Test

For the question above, my work for each of the questions is below the concerns. Here are my main concerns: Does the order in which you use the relations matter? Can you end up with less tuples with ...
1
vote
1answer
35 views

Question concerning minimal/cannonical cover

For the question above, I am confused with how to approach simplifying the left hand side of BDCE->A. Do I get rid of E, as D depends on it, or do I get rid of CD as well, as CD->A? Here's what I ...
-1
votes
1answer
38 views

Can you determine a functional dependency on a single attribute table?

If an attribute is independent is it possible for it to still have a functional dependency? For example, given these were two tables with a many to many relation: Fruit(FruitType), Blender(...
2
votes
1answer
61 views

Assessing the normal form for a relation with a multi-valued attribute

Assume that you have designed the following schema of relations: COURSES (CID, CNAME) STUDENTS(SID, SNAME, FAV_CIDS) However, you can not have a relation with set valued attributes (Did not really ...
1
vote
1answer
33 views

Is F included in F+?

The definition in my book says: The set of all functional dependencies logically implied by F is the closure of F. My question is, do we include FDs in F in F closure as well ? If I have: F = {...
4
votes
2answers
156 views

Is the inverse of Armstrong's Axioms valid as well?

I have been looking into Armstrong's axioms a little bit. In a homework[1] exercise I was asked to prove A→G is in F-closure. I managed to get it at this point: AB → GB Being at this point, can I ...
3
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2answers
38 views

Nullable, dependent attributes

I'm designing a database for students. Computer science students here in Switzerland can decide between different specializations, e.g. application development, system engineering etc. There are ...
2
votes
1answer
41 views

If A -> B is augmented with C, is AC -> B legal?

Given the augmentation axiom and the decomposition axioms of functional dependencies and a relation of R(A,B,C) with an FD of: A -> B I can augment A -> B with C to get AC -> BC. Can I then ...
0
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2answers
59 views

Insert dependent records in multiple tables, MSSERVER 2012

I'm trying to migrate Data from a Excel file to a newly build Database. I already inserted all data from the Excel file to the Database and now need to insert it in three newly dependable tables. ...
0
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0answers
45 views

Functional dependencies and normalization

I've ran into a little issue regarding functional dependencies and normalization. The thing is that I am not quite sure whether functional dependency (FD for brevity) refers to values or the attribute ...
1
vote
1answer
47 views

How to prove “A->B,C then A->B and A->C” from Armstrong Axioms

I know that this is true but I don't understand how to prove it. The Problem: Prove or disprove that if A->B,C, then A->B and A->C This answer is similar but it does not prove the relation using ...
3
votes
1answer
246 views

Transitive dependency with foreign keys

For an assignment, I had to design a database from a given problem (based on a fictional health service organisation with 3 medical centres). Three of the entities I had (among many others) were: ...
3
votes
1answer
60 views

Equivalent functional dependencies

I cannot understand why F1 is not equivalent to the other sets of dependencies below given the relation R(A,B,C): F1 = {A → B, B → C} F2 = {A → B, A → C} F3 = {A → B, AB → C} This is question no. 6 ...
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3answers
2k views

How to safely recreate a MS SQL table that has other objects depending on it?

I have a table in A Microsoft SQL 2012 database, called Courses. It was "upconverted" from an originally SQL 2000 database, upconverted to SQL 2008 database, and then upconverted again to 2012 (You ...
0
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0answers
40 views

avoiding circular dependence [duplicate]

I have following Data base design (only relevant details provided): TABLE Country COLUMN capital_city_id FOREIGN KEY (capital_city_id) REFERENCES City(id) TABLE City COLUMN country_id ...
2
votes
1answer
92 views

Does the definition of functional dependency permit derivative values?

Sorry if the question in the title seemed vague. The question is rather broad and this is the best I could summarize. I have read about functional dependency, 1nf, 2nf and 3nf. From what I ...
5
votes
1answer
732 views

Get list of functions used in a view

Say I have a Function like this: create function house_analysis(ingeo geometry) returns table(count_all numeric, count_important numeric) as $$ select count(*), count(*) filter (where h....
1
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0answers
65 views

Invalid views not showing in user_dependencies after first compilation

When I create an (invalid) view that selects from another invalid view, the view does not immediately show up in user_dependencies. I am wondering if this is expected. These are the steps to ...
1
vote
3answers
517 views

Dependency Preservation and Normal Forms

Suppose a set of functional dependencies F holds over a relation R . We find that the dependencies violate the conditions of 2NF and decompose the relation into R1 and R2. After the process what can i ...
2
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1answer
88 views

Trick question about FD's? [closed]

X Y Z x1 y1 z1 x1 y1 z1 x1 y1 z2 x2 y1 z1 The questions are : a. List all the non-trivial original functional dependencies that this relation instance preserves b. Change a single value to ...
3
votes
1answer
133 views

T-SQL to check whether or not a indexed view can be created on tableX?

After applying my database changes on the test environment, the test team starts testing their processes, one of the things I get is a truncate table error because the table is used in an indexed ...
3
votes
1answer
384 views

Functional dependencies proving method

I was having some difficulties when trying to use Armstrong axiom to solve functional dependencies. R (A,B,C,D,E,F) Given FD = { A->CD , C->BE, B->F, F->A } Prove A-> BF By using ...
0
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1answer
59 views

Multiple Functional Dependency to the same dependency

I am looking for the 3NF form of the following relation: 1. emp_no -> phone_no, office_no, dep_no, proj_no 2. emp_no, date -> job, salary 3. phone_no -> dep_no, office_no, area 4. proj_no -&...
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0answers
560 views

MariaDB/MySql Repository (Ubuntu 16.04) conflicts and more

I'm totally confused with what is going on here and have been racking my brains on this for some 4 afternoons this week. After upgrading (15.10 32bit version) to Ubuntu 16.04 some 2 weeks ago and ...
0
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1answer
200 views

How to express functional dependency in relational calculus and SQL?

I want to express in relational calculus and SQL the following functional dependency associated with Vote. This is the first time I try to implement it in actual SQL and relational calculus. Vote: #...
2
votes
1answer
65 views

What a closure `F` of a family of functional dependencies is?

I have some issues to determine what a closure F of a family of functional dependencies is. I know its definition is F⁺= {X → Y\F⊨X → Y} One example Let be the following relation R(Student,...
3
votes
1answer
356 views

checking the normal form of the current table

I have a schema R1(A,B,C,D) with the following functional dependencies A->B CD->B A->CD CD->A I need to figure out which is the highest normal form in which the following table ...
2
votes
2answers
403 views

Dependency preserving decomposition

Let be the following relational scheme: F={AB → C; AC → B; AD → E; B → D; BC → A;E → G} Is the following decomposition without loss of dependency? R¹=(A,B),R²=(B,C),R³=(A,B,D,E),R⁴...
2
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0answers
43 views

Decomposition and loss of dependencies

I'm lost in the sea with the following example of decomposition without loss of dependencies... Let be the dependencies F= {A → BC, C → AD} R is decomposed in R¹(A,B,C) & R²(A,D) I want to know ...
0
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1answer
30 views

Redundancy of information and algorithm to do lossless decompositions

Let be a relation R(NameFile, Size, Directory, DateCreation,HourCreation,Login,AutAccess,DateAccess,TypeAcces F={NF,D→S; NF, D →DC; NF, D→HC; L,NF,D→A; L,NF,D,DA,HA→TA; } Part of ...
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1answer
82 views

Applying second and third Normal Form

Let be a relation R(NameFile, Size, Directory, DateCreation,HourCreation,Login,AutAccess,DateAccess,TypeAcces F={NF,D→S; NF, D →DC; NF, D→HC; L,NF,D→A; L,NF,D,DA,HA→TA; } Part of ...
0
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1answer
32 views

Finding related functional dependencies from Amstrong's axioms

Let be F = { AB → C, B → D, CD → E, CE → GH, G → A } some functional dependencies. Do we have, thanks to Amstrong's axioms or its corollaries AB → G? My attempt I don't ...
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2answers
519 views

Relation in 2NF with a transitive dependency?

Tomorrow I have my final exam of Database Design but I have a doubt about the Second Normal Form (2NF). The definition says a relation is in 2NF if no non-prime attribute is partially dependent on a ...
2
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1answer
83 views

Determining Transitive Dependencies

I am working on figuring out partial and transitive dependencies. The Transitive ones are really confusing me because I can see a transitive dependency on nearly all of these. The partial ...
1
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1answer
316 views

Apply Definition of MVD (multivalued dependency) to Example?

Supposedly this multivalued dependency (MVD) and this functional dependency (FD): {W} ↠ {N,D} and {W} → {N} hold in this table: V W N D ================= | v | w | n | 1 | ----------------...
3
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1answer
1k views

How can I prove / disprove If A ↠ BC and A → B then A → C

/ From GATE 2007 IT: Consider the following implications relating to functional and multi valued dependencies given below, which may or may not be correct. A) If A ↠ B and A ↠ C then A → BC B) ...
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1answer
6k views

all tables used by a stored procedure and all sps that use a particular table - recursive cte

I am working on a script that gives me a list of tables that use a specific stored procedure. It also works on all tables used by a stored procedure. on the example below, all stored procedures that ...
8
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1answer
204 views

Functional dependencies applies to whole database or to a particular relation?

I am new to dbms. I saw a lecture video about functional dependencies. But I am confused a bit that whether functional dependency is a constraint put on whole database or on a particular schema?
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0answers
61 views

Managing View Dependencies

I am using PostgreSQL and I am adding a single column to a view. Unfortunately, I will have to drop and recreate that view as well as the 9 other views that are dependant on the view. What ...
0
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1answer
636 views

Find the functional dependencies that hold in a relation

There is a question in my book that asks the following: Suppose we have relation R ( A ,B ,C ,D ,E ) , with some set of FD’s, and we wish to project those FD’s onto relation S(A, B, C). Give the ...
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vote
1answer
1k views

Decompose table into third normal form

Tables X and Y are given as below : X (A, B, D, E, F, G, H, J) with A and B as primary key Y (K, L, M, N, O, P, Q, R) with K and L as primary key Now we need to decompose these tables into tables in ...
2
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0answers
262 views

Is the table in 3NF?

I am creating a relational database - a library management system. I want to show an example where I normalize the data from 2NF to 3NF. My example of 2NF looks like The definition of third normal ...
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1answer
57 views

Determining Functional and Transitive dependencies from Relational Model (with no sample data)

I have a relational model which I've converted from an EER diagram... I've been asked to find the functional and transitive dependencies but how does one do that when there's no sample data to start ...
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1answer
199 views

Listing column dependencies

I want to alter the datatype of a table column from varchar(x) to varchar(y). To do that, I need to know what dependencies there are on this column. Any suggestions?
2
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1answer
317 views

If A and B are candidate keys, then AB is candidate key or not ?

If R{abc} is a relation, f{ a->b b->a a->c b->c }, then a and b are candidate keys. What about ab ? Is it a candidate key or is it a super key or both ?
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0answers
243 views

testing an extraneous attribute in a relation using functional dependency

I am studying the book "Database System Concepts" by sudarshan . In chapter 8.4.3 in a dependency alpha->beta , If A ∈ aplha to check if A is extraneous, let (gamma = alpha − { A}), and check if (...
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1answer
42 views

Dealing with co-dependent not null columns

Say I have a table entities (subclassed by people and organizations tables), where each entry requires a primary_email_id. The entities table looks like this: entities ======== id INT AUTO_INCREMENT ...